ASTM D790 Testing Services
ASTM D790 is one of the most commonly used materials tests in the plastics industry. It measures flexural properties related to stiffness, bending and resistance to deflection. This helps engineers and manufacturers compare materials before they are used in finished products.
Teams commonly request ASTM D790 testing for material comparison, product design validation, supplier qualification, production quality checks or failure investigation. If a plastic, polymer or composite part may bend under load, ASTM D790 flexural test data can help determine whether the material is appropriate for the application.
What ASTM D790 Measures
The ASTM D790 test determines the flexural (bending) properties of reinforced and unreinforced plastic, electrical insulation materials and high-modulus composites.
The test uses a universal testing machine and a three-point bend fixture to bend material at a rate proportional to the test specimen's depth. The test material used in ASTM D790 testing is typically a rectangular bar molded directly or cut from sheets, shapes or plates.
ASTM D790 tests the following properties:
- Flexural modulus: Flexural modulus, also known as tangent modulus, measures the material's stiffness. It is the slope of the initial linear portion on the load-deflection curve.
- Flexural stress: Flexural stress describes the stress calculated in the specimen during bending at a given load.
- Flexural strength: Flexural strength is the maximum flexural stress measured during a bend test.
Materials Commonly Tested Under ASTM D790
ASTM D790 is commonly used to measure how rigid and semi-rigid plastics respond when they are bent. This makes it useful for polymer bend testing when manufacturers need ASTM D790 flexural test data for:
- Molded plastics
- Machined plastic bars
- Polymer sheets
- Reinforced plastics
- Composite materials
- Electrical insulation materials
The test is especially useful when a material may experience bending, deflection, or stiffness demands in service. For example, a plastic housing, panel, structural component or insulating part may need to resist bending without excessive deformation. ASTM D790 testing helps document that behavior in a controlled laboratory setting.
Since different materials can respond very differently under load, the test can be used for both early- and late-stage quality review. It can also help compare alternate suppliers, resin systems, fillers, reinforcements or production lots.
ASTM D790 Specimen Preparation
Exact specimen requirements, including ASTM D790 specimen size, depend on the material and project specifications. However, proper preparation is done to make sure that the measured performance reflects the material itself rather than variations in samples.
Here’s what you need to know about specimen preparation for ASTM D790 testing.
Sample Geometry and Dimensions
ASTM D790 is typically performed on rectangular bar specimens. ASTM D790 dimensions, support span and loading setup are selected according to the standard and the material being evaluated.
These specimen dimensions, especially thickness, have to be consistent because the geometry affects bending behavior, stress, strain, and ASTM D790 flexural test results.
Specimens may be molded directly or machined from sheets, plates, or other stock materials, depending on the project and material being tested.
Conditioning Requirements
In some cases, specimens may need to be conditioned before ASTM D790 testing. Conditioning requirements can depend on the material type, customer specification or intended application.
When applicable, conditioning helps establish a consistent testing basis by controlling factors such as temperature, humidity or moisture exposure that could influence flexural performance.
The Importance of Consistent Specimen Thickness
The specimen thickness must be consistent because variations in thickness can affect stiffness, stress calculations, and the overall test results.
Using specimens with uniform dimensions helps improve result consistency and allows you to have meaningful comparisons between materials, production lots or design variations.
Why Improper Preparation Can Affect Results
- Dimensional inconsistencies can alter how the specimen bends during ASTM D790 testing, leading to inaccurate flexural property measurements.
- Surface damage such as scratches, nicks, or gouges can create stress concentrations that affect how and where a specimen fails.
- Machining defects can affect load distribution and produce results that do not accurately represent the material’s true performance.
- Failure to follow required conditioning procedures can change material properties, leading to test data that is not representative of the expected performance.
Three-Point Bend Testing Procedure
The ASTM D790 flexural test uses a three-point setup. During the test, the specimen is supported at two points while force is applied at the center using a loading nose. This creates bending stress in the material rather than pulling stress.
As the load is applied, the ASTM D790 testing equipment records how the material bends, deflects, or breaks. Some materials may fail suddenly. Others may bend significantly before reaching the end of the test.
The recorded data helps to show how stiff the material is, how much stress it can withstand and how it behaves as the bending load increases.
ASTM D790 Bend Test Method Options
ASTM D790 includes different procedure options depending on the property being measured and the material being tested. Procedure A is commonly used when flexural modulus is the primary focus, while Procedure B may be used when flexural strength is the primary focus. The appropriate test speed and setup should be selected based on the standard, specimen geometry, and project requirements.
ASTM D790 specimens are typically rectangular bars, but the required dimensions depend on the material, specimen thickness, support span, and project specification. VTEC Laboratories can review your sample details and help confirm whether the submitted specimens are appropriate for testing.
During the test, we lay your test bar on two support spans and use a loading nose to place your load midway between the two supports. The ASTM D790 flexural test continues until the specimen breaks, yields, or reaches the strain or deflection endpoint required by the selected procedure and project specification.
Flexural Strength vs. Flexural Modulus
Flexural strength and flexural modulus are related, but they do not describe the same material behavior.
ASTM D790 flexural strength describes how much bending stress a material can withstand during ASTM D790 testing. It is often used when engineers need to understand resistance to bending failure or maximum stress under the test conditions.
Flexural modulus describes stiffness. A material with a higher flexural modulus generally resists bending more than a material with a lower flexural modulus. This can be important for parts that must hold shape, limit deflection or support loads without becoming too flexible.
In practical terms, flexural strength helps answer, “How much bending stress can this material handle?” Flexural modulus helps answer, “How stiff is this material when bending begins?” Many projects need both values to support design review, material comparison or quality control.
How ASTM D790 Testing Results Are Reported
An ASTM D790 flexural test report can include flexural strength, flexural modulus, stress-strain behavior and other relevant observations from the test. Where applicable, the report may also note how the specimen behaved during loading, including whether it broke, yielded or continued bending through the test.
These results give engineers and product teams practical data that they can use in material selection, design review, supplier comparison and production quality checks.
For example, a team may compare two polymer grades to see which one offers better stiffness, review whether a production lot is consistent with prior results or use the data to support customer documentation.
The value of ASTM D790 testing is its ability to compare material behavior under a predefined bend testing method so that decisions are based on measured performance rather than assumptions.
ASTM D790 vs. ASTM D638
Feature |
ASTM D790 |
ASTM D638 |
| Primary Focus | Bending or flexural performance | Tensile performance |
| What It Measures | A material’s stiffness, bending strength and resistance to deflection. | How a plastic material behaves when pulled in tension. |
| Typical Use | ASTM D790 testing is used when flexural properties and bending behavior are needed. | When tensile properties and tensile behavior of plastics need to be evaluated. |
Some projects require both the ASTM D790 flexural test and the ASTM D638 test because real parts may experience more than one type of load. If your project requires both flexural and tensile data, VTEC Laboratories can help you review the appropriate testing path.
Industries Using ASTM D790 Testing
- Plastics Manufacturing: Used to compare resin grades, suppliers and production lots for consistent flexural performance.
- Composites Manufacturing: Used to evaluate the stiffness and bending behavior in reinforced composite materials.
- Aerospace: For verifying that components maintain structural integrity under bending loads.
- Automotive: To assess the flexural performance of plastic and composite vehicle components.
- Construction Products: To measure the bending resistance of panels, boards and polymer-based building materials.
- Consumer Products: To confirm sufficient stiffness or reliable everyday product performance.
Why Choose VTEC Laboratories for ASTM D790 Plastic Bend Testing?
VTEC Laboratories has been a leader in materials testing for over 30 years. We've performed countless ASTM D790 tests during this time, including bend testing for plastics, delivering accurate results and some of the fastest turnaround times in the industry.
VTEC Laboratories provides physical testing like ASTM D790 through experienced lab personnel and established quality procedures. Our team can review sample details, confirm project requirements, and provide clear reporting to support material comparison, design review, quality control, or documentation needs. Ask our team about current turnaround timelines and rush options when requesting a quote.
Your report will include our analysis and recommendations to address any issues our scientists detect. You'll get the data you need to make an informed decision about which materials will work best for your application.
How to Request ASTM D790 Testing
It helps to provide as much practical project information as possible when you request the ASTM D790 flexural test. Some useful details to include are:
- Material type
- Intended application
- Required standard or customer specification
- Number of specimens
- Whether the testing is needed for QA, R&D, compliance documentation, comparison testing or failure investigation
You should also mention whether the specimens have already been prepared or whether you need guidance on sample size, geometry or submission requirements.
If your project involves customer specification, drawing, purchase order requirement or internal quality procedure, include that information too with your request.
Contact Us for ASTM D790 Testing Services
VTEC Laboratories is your trusted source for ASTM D790 testing. Contact us today to request a free quote or discuss sample requirements.
Learn More About ASTM D790 Flexural Testing Services
At VTEC Laboratories, our role as a multi-functional company stems from our more than three decades of experience. Due to our extensive expertise in multiple industries, we provide comprehensive services like ASTM D790 at our lab that meet each field’s unique standards, needs and objectives.
Learn more about our services by contacting us online or calling us at (718) 542-8248.
VTEC Laboratories Inc.
Since 1982, VTEC Laboratories has provided fast, reliable testing services across aerospace, construction, and manufacturing. Based in New York, we offer ISO-accredited fire, weathering, industrial, and environmental testing delivered with speed, accuracy, and clear communication.
212 Manida Street, Bronx, NY 10474
Phone: 718-542-8248
Fax: 718-542-8759
